Spark plug



Sept. 29, 1925. 1,554,996

L. w. G. FLYNT SPARK PLUG Filed Nov. 3, 19m

A Patented Sept. 29, 1925.

fUNlTED STATES PATENT OFFICE.

LOUIS W. G. FLYNT, OF NEWARK, N EW JERSEY.

SPARK PLUG.

Application led November v3, 1921. Serial No. 512,438..

To all whom it may concern:

Be it known that I, LOUIS W. G. FLYNT, a

subject of Great Britain, residing at Newark, in the county of Essex and State of New Jersey, have invented new and useful Improvements in Spark Plugs, of which the following is a specification.

This invention has for one of its objects the provision of a gas' tight joint between the insulatorl and the metal body of the plug without the interposition of gaskets or packing material of any kind together with means for readily disassemblingthe insulator from the metalbody to permit cleaning or inspection.

A further object is the provision of an adjustable gap in the center electrode for the purpose of intensifying the igniting spark, in such a position vas to permit visual examination of the -spark that jumps the gap together with means for preventing the intensilier spark from igniting inflammable gases or liquids that may come into. contact with it, consisting of a transparent tube so mounted in the insulator as to form a flame condenser.

These and other objects, which will late-r become apparent, are attained'by the novel design, construction and arrangementv of parts hereinafter described and shown in the accompanying drawing, forming an essential part of this* vdisclosure and in whichz- Figure 1 is a longitudinal sectional vie taken through the center of a spark plug made in accordance with the invention.

Figure 2 is a transverse sectional view taken on line 2`2 of Fig. A1.

Figure 3 is a similar sectional view taken on the line 3-3 of Figure 1.

Referring to the drawing in detail, the `numeral 10 designates the main cylindrical portion of the plug body, the same having a hexagonal upper portion 11 suited to receive a wrench in securing the, plug in operative position and a shoulder 12 at its axial cylindrical bore 17 at the bottom of the body, merges into the smaller end of a-conical-recess 18, the larger, inverted base end of -which is approximately `\i\n the plane of the upper end of the body 10, and above this recess the body is internally screw-threaded as at 19.

Fitting these threads is va clamp ring or annulus 20, its outer projecting end being formed into a hexagon head 2Oreceptive of a wrench in making adj ustment,'its'inner end being provided with a beveled counterbore the purpose of which shall presently appear.

The insulator is comprised of a conical portion 21 having two or more slightly raised rings 22 and 22', preferably finished by grinding to accurately fit the conical recess 18, the lower ring being midway in the length of the cone which terminates at a point above the cylindrical ope-ning 17.

The upper contact ring 22 merges into a short cylindrical portion 23 necked as at 24 to a reduced diametered portion 254 which extends to aconsider'able height above the annulus or clamp ring 20-20", 4through which it freely passes and tern'iinates in a level top `26 having rounded corners as shown.

ADisposed. on the seat formed by the neck 24, is a metal ring 27, preferably of an alloy of aluminum having a high coefiicient of expansion, the same being centered by the beveled contactsurface of the clamp ring 20 whenpressure is brought to bear upon it in order that the pressure transferred tothe insulator may be in a vtruly axial direction yand thus result in a uniformly distributed pressure on the ground surfaces of the steel body and the insulator where they contact to make a gas tight joint, as hereinbefore described. Pressure brought to bear on the metal ring 27 by the clamp ring 20 will circumferentially stress the clamp ring thus permitting its elasticity to assist the metal ring 27, which has a higher expansion coefficient than the metal of which the plug body, 10, is made, to compensate for the expansion differences of the plug body and the insulator.-

Formed in the insulator, at its lower end, is an axial passage 28 having a step ed reduced upper portion 29 into which eads a small central opening 30. l

Tight fitted tothis opening is the upper element 31 of an insulated conductor having l a conical point 32 .at its upper end an enlarged portion 33y which extends down through the passage 29 and 28 to a point adjacent the angularly turned conductor 1G.

The element 3l may also be held in fixed relation to the insulator by cement but preferably depends upon a frictional fit in it. t

Freely fitted into a recess 34 formed 1n the upper portion of the insulator is a transparent tube 35, into which the conical point 32 of the conductor extends to about the center of' the length of the tube and at which point a plurality of radial openings 36 are formed thru the insulator permitting it to be seen. i

It is found iu practice that intensifier sparks of the class described do not function properly if hermetieally sealed and that ventilation is required. A freely exposed spark is liable to ignite stray inflammable vapors or fluids, with consequent danger, but the surrounding of the sparking points with a loosely fitted transparent tube, such as 35, perm'its the necessary ventilation but `prevents the escape of fiame generated by the spark on the inside of the tube by making its only passage to the outside thru narrow spaces whose walls are relatively cool so that they form a flame condenser.

Above the recess 34 the insulator is formed with internal screw-threads suited to receive a. metal plug 37 having a flanged head 38 through which passes an axial screw 39 having a conical point 40 registering with the point 32 of the lower conductor and adjustable therewith by the nut 41, on the upper surface of which may be disposed the usual type of electric connection (not shown) the ysame being secured by the knurled head nut 42 threaded adjustably on the extending end of the screws 39.

In operation, the parts having been assembled as indicated and suitable electrical connections having' been made respectively to the spark plug support and screw section 39 of the plug, current will pass through the conductors, the spark passingthrough the gap between the points 32 and/l0 being visible to an operator.

It will be obvious that the intensity of the spark may be measurably increased or diminished by proper adjustment of the distances between the points and that the operative sparking will take place as usual at the terminals 16 and 32.

It will also be apparent that a firm and secure construction has been set forth, that the insulating element is Well protected against damage, and further, that due to the air space surrounding the major portion of the lower conductor, it is less liable to collect carbon than where a relatively short end is exposed.

Although the foregoing is descriptive o the preferred embodiment of the invention, it will be apparent that minor changes may be made in its construction, Without the exercise of invention 'or conflicting with the scope of the claims hereto appended.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is

l. A spark plug comprising a body having a conical cavity, an insulator, a raised upper and lower ring on said insulator accurately fitting the cavity, means for clamping said insulator to said body, and a spli-t,soft metal ring having a high coefficient of expansion interposed between said vclamping means and said insulator.

2. A spark plug comprising. a body having a conical cavity, an insulator, a raised upper and lower ring on said insulator accurately fitting the cavity, means for clamping said insulator to said body, saidV means being provided with a beveled counterbore,`and a split, aluminum ring having a high coefficient of expansion interposed between said beveled counterebore and said insulator.

8. A spark plug comprising a body having a conical cavity, an insulator, a raised upper and lower ring on said insulator accurately fitting the cavity, means for clamping said insulator to said body, and a split ring of an alloy of aluminum having a high coefficient of expansion interposed between said clamping means and said insulator.

4. A spark plug comprising a body having a conical cavity, an insulator, raised rings on said insulator accurately fitting the cavity,`

means for clamping said insulator tol said body, a conductor Xcd in said insulator, said conductor being unconfined for the greater portion of its length and a split aluminum ring having a high coefficient of expansion between said insulator and said clamping means for producing a gas-tight Join This specification signed this eighteenth vday of October, 1921.

LOUIS W. G. FLYNT.

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